P&H Foundation Systems 2011

Patrick and Henderson Foundations 4/3/2011

© 2011 Earth Systems Global inc. 1

P&H Foundation Systems

By Shelton L. Stringer, PE, GE, PG, EGEarth Systems Global Inc.

© 2011 Earth Systems Global Inc.

The Patrick and Henderson Tensionless Pier (P&H Pier)

The P&H Pier consists of a large, cast-in-place pierThe P&H Pier consists of a large, cast in place pier foundation to support monopole towers

(US Patent No. 5,586,417, Canadian Patent 2205502, Chinese Patent 201020166104.7).



Advantages of the P&H Pier

P&H foundations are the most economical available for wind turbine support.

– 25% to 35% less than the cost of a gravity spread foundation

– About 3% to 6% savings in total project development costs

P&H foundations are the most environmentally green.

– The smallest footprint available, with far less ground disturbance than a gravity spread foundation

– Uses far less total concrete and steel than a gravity spread– Uses far less total concrete and steel than a gravity spread foundation with much quicker assembly

Fewer materials make the P&H foundations a more attractive ecological and environmental solution for foundation support.

A smarter choice

P&H Foundations Built Supporting Wind Energy Projects

27 States, 5 Provinces4900+ Built

28 States, 5 Provinces

4200+ since 2000149 Projects

Earth Systems Southwest

5700+ Built

200+ Projects



SNYDER WIND ENERGY PROJECT Scurry County, Texas

Tallest wind turbines in the United States dto date.

Height to Blade Tip = 150 m, 492 feet!

21 Vestas V90 3.0-megawatt wind turbines on 105 m towers.

P&H pier foundations 40-feet deep

Used Anderson Drilling “Big Stan” 18-foot diameter auger rig.

BUFFALO MOUNTAIN WIND ENERGY PROJECT Anderson County, Tennessee

Tennessee Valley Authority project

15 towers Vestas V80 1.8-MW turbines on 80-meters towers

P&H Pier foundations are onfoundations are on reclaimed land from coal mine spoils



P&H Pier Construction in China 内蒙古,中国, 2009

4/3/2011 7

2 - Goldwind 750 kW Turbines in Inner Mongolia

中国金风科技内蒙古达茂，2台750KW风机，目前已经并网发电。

Construction of the P&H Pier

Construction of the pier begins by digging a hole with an excavator or drill rig. Rock sites require controlled pre-blasting.

Typical depth 25 to 34 feet y(7.5 to 10.5 m)

Cranes set an outer corrugated metal can (CMP) in the hole, typically 12 to 16 feet diameter (3.7 to 4.9 m).




Sand-cement slurry is placed as backfill between the outer CMP and the excavation sides.

Threaded steel rods (encased in PVC sleeves) are arranged with a template that matches the base flange of the tower.

These rods are set and bolted to an embedment ring within the annular space between CMP cans.

– A smaller, inner CMP is set


concentric within the hole, typically 10 to 12 feet diameter (3.0 to 3.7 m).

– A lower plug of concrete and the excavated spoils are placed within the inner can.

– Foundation concrete is placed between the two CMP cans, forming a hollow cylinder. A concrete floor slab and top collar is cast.




The tower is bolted to the threaded rods extending above the concrete.

The grout trough beneath the base flange is filled.

The rods are post-tensioned to keep the concrete inkeep the concrete in compression (hence tensionless) during loading.

How the P&H Pier works

The lateral and moment capacity i d l d b id b iis developed by side bearing as the rigid pier is free to rotate within the earth.

The ultimate passive resistance is dependent on the shear strength of the surrounding soil or rock (friction angle, and cohesion, c).

Pier rotation and deflection are dependent on compressibility of the soil or rock, expressed as a non-linear, load-deformation (p-y) curve.



Key Geotechnical Issues The geotechnical report for the project

is the basis for the properties of theis the basis for the properties of the soil or rock in analyses.

Overturning stability with a global safety factor of at least 2 against extreme loads

Pier rotations and deflections should remain within a tolerable rangeremain within a tolerable range– typically, 2 to 5 mm operational, – 10 to 20 mm extreme– 1 mm/m rotation – operational– 3 mm/m rotation - extreme

Foundation rotational stiffness to avoid resonance and excessive vibrations

Design Loads

Loads come from the wind turbine manufacturer based on IECIEC.

Typical Extreme Wind Loads (unfactored):– Axial 140 – 575 kips (700 - 2550 kN)– Lateral 70 – 200 kips (300 – 900 kN)– Moment 10,000 to 58,000 ft-kips (14 - 78 MN-m)

Seismic loads, even in moderate seismic regions, are Seismic loads, even in moderate seismic regions, aregenerally less than design wind loads

– Exception: 2010 California Building Code, active faults, < 10km, non-building structure, minimum design force controls,CsW = 0.8S1/(R/I) - San Andreas & Garlock faults.

– GL & IEC Rules of applying EQ + Operational Load



Important factor for

Rotational (Rocking) Stiffness

Important factor for performance of wind turbine foundations

Rotational Stiffness, K= M/, where

M = moment,

t ti

M

Greatly exaggerated rotation from FEM

= rotation

Normal requirement: K= 20 to 60 GN-m/radian

3D Finite Element Modeling (FEM)

Half Model

Tower

P&H Pier

Loading at Top of Tower

Ground



FEM ResultsLateral D f tiDeformation of Pier

Tower Frequency Verification Testing

Frequency response of tower q y precorded by accelerometers, displacements recorded by transducers

Tower frequency changes when considering Soil-Structure Interaction

The wind turbine natural frequency should be a margin away from the rotor rotation frequency to avoid dynamic amplification.



P&H Rock & Pile Anchors Foundations

Guantanamo Bay, Cuba 20044 – NEG-Micon 950 kWon P&H anchorfoundations usingfoundations usingCon-Tech self-drillinganchors in conglomerate



Hull II Wind Project, Massachusetts

Hull II Wind Project 2006

Vestas V-80 1 8MW turbine Vestas V-80 1.8MW turbine on 80-m tower

67 feet of landfill over dense rock

Supported on P&H pile anchor foundation

Piles driven to rock and rock anchors extendedrock anchors extended below

Two rows of piles

Featured at 2006 AWEAConference



Locust Ridge, PennsylvaniaGamesa 2.0 MW turbines on rock anchor foundations

Setting the anchor bolt cage g gshown at right

Placing concrete for cap shown below

Ground Anchor Components

Unbonded length Unbonded length (free stress zone)

Bonded Length

Anchor or Tendon

Grout

Anchor Head & Bearing Plate



High Strength Anchor Bars

PTI Proof Testing & Maintenance Checks

Initial Proof Test each bolt to 133% of design load (DL)

Periodic Maintenance Program to check and retension anchors at 3 months and 1 year



TheThe P&H Pile Anchor Foundation

US Patents 7,533,505 & 7,618,217Chinese Patent 201020166104.7

Note Void (gap) between cap and pile anchor

Mind the Gap

Di t d Pil F d ti Disconnected Pile Foundation

No structural connection between anchor and cap

The gap is the key

Gap allows post-tensioning of anchor and retensioning

Pile Anchor uplifts and cap compresses the subgrade

Post-tensioning improves subgrade modulus by confinement and compression

Documents

P&H Foundation Systems 2011